Locking device for systems access to which is time-restricted

ABSTRACT

The present invention relates to a locking device 2 for objects of use, which are to be used for a particular period of time by a user, whereby the locking device 2 opens after the input of an opening code 4. The locking device is distinguished in that after input of an end code 6 the locking device issues a confirmation code (8) and changes the opening code in a particular manner (4→4&#39;). Further, the invention relates to a method for the controlled, time-restricted, use of objects of use, which employs the locking device 2. In this method, an opening code 4 is issued by an access control unit 1, the opening code 4 is input into the locking device 2 for opening the same, an end code 6 is input for ending the use and then a confirmation code 8 is issued, the opening code being altered (4→4&#39;) by means of the locking device 2.

BACKGROUND OF THE INVENTION

The invention relates to a locking device for objects of use, to be usedfor a restricted period of time, and a method for the controlled use ofthe objects of use.

Electronic access authorization systems offer, in comparison withmechanical locking systems, a much higher degree of flexibility in theindividual issue and withdrawal of access authorizations.

Many different forms of such electronic access authorization systems areknown which employ differing communications procedures andidentification means, these includes for example cards, magnetic cards,chip cards, processor chip cards, transponders and the like, whereby thedata exchange takes place via electrical contacts, electromagnetic orinfrared signals and the like. Further, there are known combinationlocks which are operated by the entry of codes via a key pad and whichemploy particular protocols and algorithms for control andreprogramming.

The principle of code switching, which brings about an increase insecurity against improper information monitoring (bugging) is found in aseries of publications such as e.g. DE 27 35 048 C2 or DE 43 25 137 A1.However, these systems are based upon the employment of intelligentkeys, equipped with memories.

DE 30 31 405 and a series of similar systems, which are based uponsophisticated code conversion methods, involve storage of accessauthorization relationships in the lock or in a key.

With all such systems it is disadvantageous that the checking of theaccess authorization of the user takes place directly and locally in thelock itself, so that the access authorization information must be storedin the lock and/or in the key. This brings about the following problems:

The loss of a key means that there is a risk of misuse for all lockswhich the key fits. In the case of loss, these locks must all be soreprogrammed, at their locations, that the lost key is in futurerejected.

The same applies to key-less systems which work only with the input ofcodes via a keyboard, in the case that a code becomes known or isdetected by improper monitoring (bugging).

It is further disadvantageous that the programmed access authorizationrelationship can be checked or changed only with difficulty, because alllocks concerned and/or keys must be checked and reprogrammed. The effortinvolved thus increases rapidly with increasing complexity of the accessauthorization relationship between users or keys or codes and locks, andrequires a high level of organisation.

In DE 20 58 623 there is described a device which overcomes theabove-mentioned disadvantages in that the access relationship isadministered in a central access control unit, whereby, however, acabling the locks with the access control unit is necessary, which is ofdisadvantageous.

In DE 24 01 602 C2, which is most closely related to the invention setout here and which likewise employs a central code issuing device anddecentral locking devices, the significant disadvantage of a need forcabling is removed. There is described a method for the alteration oflock combinations specifically for use in hotels, which is based uponthe fact that the end code of a cycle n is the same as the opening codeof the cycle n+1, so that the first input of a new code deactivates theold code.

With regard to employment in a hire system, it is howeverdisadvantageous with this system that the end of the cycle of use cannotbe determined by the current user but only occurs with the beginning ofthe next cycle of use; that is, is initiated by the next user. Thismeans, inter alia, that the current user cannot prove that his currentcycle of use has ended. This, however, excludes employment in a hiresystem. It is further disadvantageous with this system that problems canappear when the code issuing unit and a locking device "get out ofstep"; that is, are no longer synchronized.

In DE 43 01 039 C2 there is described a method for the release ofvehicles for a particular user, dependent upon a reservation. This,however, requires high technical outlay (cordless telephone) in relationto the object of the use, and fixed parking places in the vicinity ofhire stations.

SUMMARY OF THE INVENTION

One object of the invention is to make available a locking device forobjects of use, which are to be used for a particular period of time bya user, which avoids the disadvantages of the described locking devices.

A further object is to make available a method by means of which thecontrolled, time-restricted use of objects of use is made possible.

In accordance with the invention, this object is achieved by a lockingdevice for objects of use, which are to be used for a particular periodof time by a use, whereby the locking device opens after the input of anopening code. After input of an end code, the locking device issues aconfirmation code and changes the opening code in a particular manner.Further, in accordance with a method for controlled, time-restricted useof objects, an opening code is issued by an access control unit into thelocking device, and an end code is input for ending the use. Aconfirmation code is then issued, and the opening code is changed.

Further features and advantages can be understood from the followingdescription.

BRIEF DESCRIPTION OF THE DRAWING

Below, the locking device in accordance with the invention will bedescribed with reference to an exemplary embodiment and with referenceto the drawing, which illustrates a locking device in accordance withone embodiment of the invention.

DETAILED DESCRIPTION

A locking system consisting of one or more locking devices 2 and one ormore central access control units 1 is illustrated in the drawing.

The locking device 2 works with four codes, namely a code request code3, an opening code 4, an end code 6 and a confirmation code 8.

The codes are entirely or partially variable in such a manner that theychange completely or partially with each cycle of use. This principle isknown as code switching.

Each cycle of use extends from the first opening by means of the firstinput of the opening code 4 up to the final locking through the input ofthe end code 6.

The code switching protocol is secret and known only to the lockingdevice and the access control unit. Between the codes there maypartially be a secret relationship such that in fact only one of thecodes is altered in accordance with the code switching protocol and theother codes are consequently partially adapted so that they againsatisfy the secret relationship.

The codes and the code switching protocol thereby have the propertythat, even when observed over many cycles of use, a relationship betweenthe codes of a user cycle amongst one another or between the codes ofsuccessive user cycles cannot be determined or can only be determinedwith very great effort. The code switching protocol or the relationshipbetween the codes one to another is thereby, ideally, different for eachlocking device, so that breaking of the code can only cause limitedconsequential damage.

The code request code 3 consists, in the simplest case, solely of afixed object or locking device number. It need not be variable, but itcan usefully be variable. It serves, so far as it is variable, on theone hand as information for a potential user, who with the object beforehim can determine therefrom whether this object is presently in use. Onthe other hand, it identifies the use cycle and use condition andcommunicates as initial input information to the access control unit 1not only which locking device 2 is to be opened but also in which usecycle and condition this locking device is at present. This increasesthe reliability of the synchronization of the locking device 2 with theaccess control unit 1. The code request code 3 can, moreover, includeadditional data concerning the condition of the object of use, such ase.g. an initial counter value or the like. This additional data shouldthereby be encrypted, as protection against manipulation, or be securedby means of an encrypted check sum.

The opening code 4 corresponds to a temporarily valid key and controlsthe opening of the lock; that is, the release for use of the objectcontrolled by the locking device 2. When it is input, the lock opens andthe object can be used. This applies exactly for the period of thecurrent cycle of use; that is, if appropriate, for a plurality ofopening procedures, whereby a temporary re-locking of the lock withoutcode, e.g. by means of mechanical locking or a simple key signal, cantake place. With the expiry of the use cycle, the opening code 4 losesits validity, due to the code switching. The opening code 4 mayexpediently contain additional information, originating from the accesscontrol unit 1, intended for the object of use, by means of which e.g.the number or the kind of use procedures for the object of use, or theperiod of use, can be restricted. This additional data also shouldthereby be encrypted, to protect against manipulation, or secured bymeans of an encrypted check sum.

The input of the end code 6 marks the end of a cycle of use. Upon inputof this code, the lock device must either already be in the lockedcondition or it goes into the locked condition. The confirmation code 8is issued and the code switching effected (4→4') An opening anew is thenonly possible given the request of the new opening code 4' from theaccess control unit. The end code 6 may consist solely of a simplesignal, which indicates the end of the cycle of use. Expediently,however, this should only be actuable by the legitimate user; thus theend code 6 should only be accessible or known to this legitimate user.The end code 6 may thereby expediently stand in a simple relationship tothe opening code 4, for example the opening code 4 in the reverse orderor consist of an additional number and the opening code 4, or it can beequal to the opening code, but thereby only have its effect as end code6 through actuation of an additional signal.

The confirmation code 8 is provided for the final input into the accesscontrol unit 1. In relation to the access control unit 1 it serves asproof of the ending of the use of the object of use controlled by thelocking device 2, releasing the user from responsibility. Thisconfirmation code is of significance in particular in the case ofemployment in hire systems. Also this confirmation code 8 canexpediently include additional data, e.g. concerning the distancetravelled or number and kind of employed functions of the object of use,which then can be evaluated or stored by the access control unit 1 forthe purpose of billing. The billing may consist e.g. in the return of apreviously made deposit, less the use fee. For this additional dataalso, securing by encryption or by means of an encrypted check sum isrecommended.

The transfer of codes between access control unit 1 and locking device 2may be effected by means of electromagnetic signals, such as e.g.infrared signals, entirely without involvement on the part of the user.

Equally possible is the employment of different kinds of carrier mediafor carrying the codes into the hands of the user. Conceivable ascarrier mediums are magnetic cards, chip cards, processor chip cards,magnetic coded paper strips, paper strips with punched hole patterns orprinted bar codes, modified infrared-signal-controlled automobile keysand the like.

In entirely or partially manual embodiments, the code transfer could beeffected by means of simple reading from LCD displays and input viakeypads.

In all variants, for bridging larger distances, the transfer of codescan be effected in part via a telephone line.

The proof of authorization of the user with regard to the access controlunit 1 can be effected in accordance with a method known from the stateof the art, e.g. via a magnetic card or a chip card or a processor chipcard or a biometric procedure or an exchange of coded signals, e.g. bymeans of an infrared signal key module or by means of the simple inputof a secret code via a keypad. The access control unit 1 can therebyexercise various functions. This extends from the simple receipt of adeposit with final return of a remainder amount, up to storing of alluse procedures and billing by way of a bank account.

In the following the method in accordance with the invention for thecontrolled use of objects of use will be described with reference to anexemplary embodiment and with reference to the drawings:

The code request code 3, which may contain (encrypted) status data ofthe object of use, is taken from the object of use which is intended tobe used, or from the locking device 2, and entered into the accesscontrol unit 1, whereby the locking device 2 to be opened and ifappropriate its condition is identified. Additionally, with respect tothe access control unit 1, it is determined (9) in accordance with amethod corresponding to the state of the art whether the authorizationfor opening the locking device 2 identified by the code request code,and thus the authorization for use of the corresponding object of use,is confirmed and if appropriate that a deposit has been paid. In thecase of a positive result of this check, the currently valid openingcode 4 for the locking device 2, in which there may be contained alsoadditional data for evaluation by the object of use and the control unitof the same, is issued.

This is entered into the locking device 2, whereupon the lock opens (5)and the object of use can be used. A temporary re-locking and re-openingwith the opening code 4, e.g. in the case of vehicles, is possibleduring the use cycle. The code request code 3 can be modified for theduration of the use cycle in such a manner (3→3*) that for a user whocomes across a locked object of use it is apparent that this object isalready in use.

If the use is to be ended, the end code 6 is entered. This canexpediently consist e.g. of the opening code 4 in combination with anadditional signal. If necessary, the locking device then goes into alocked condition (7), insofar as it is not already in such a condition,issues the confirmation code 8 and so switches itself by means of thecode switching that further use is possible only if another new openingcode 4' is requested. The confirmation code 8 can again be entered intothe access control unit 1, whereby the end of the use of the object ofuse can be determined, to release the user from further responsibilityfor the object of use, and if appropriate with the aid of additional(encrypted) data contained in the confirmation code 8 there can beeffected a final billing, such as e.g. the return of a deposit or thelike. The request code 3* can, thereby, be so modified (3*→3') that fromthis code it can be clearly determined on the one hand that a new usecycle has started and on the other hand the condition (not in use) canbe clearly determined. This ensures the synchronization of the lockingdevice 2 with the access control unit 1. Expediently, the new coderequest code 3' may be the same as the previous confirmation code 8.

The advantages of the invention are the following:

On the one hand, the user can himself determine the end of the useprocedure, and on the other hand can prove that the use has ended. Theseare important prerequisites for a hire system, which the above-describeddevices and methods of the state of the art do not fulfil.

The synchronisation between locking device and access control unit isensured by means of the employment of the code request code 3, which isnot the case with the above-mentioned, known methods.

For the locking devices 2, of which a number are present, a cheap, lesssecure code input/output method can be chosen, e.g. a simple keypad anda simple LCD display, but in contrast there can be selected for the useauthorization check 9, with regard to the access control unit 1, ofwhich as a rule only one is present, a more complex, expensive method,such as e.g. a processor chip card.

The logic to be implemented in the multiply present lock devices 2 isvery simple and consists in substance only of an opening code comparisonand a code switching algorithm, which makes possible economicalmanufacture.

Security is high, because improper monitoring (bugging) of thecommunication with the locking device 2 can scarcely cause damage, sincethe information obtained becomes of no value with the ending of the usecycle. Since possibly employed keys (carrier mediums for code transfer)have only temporary validity, a loss of the same does not involveconsequent greater damage or lock reprogramming, as is the case withsystems having permanently valid keys.

An information connection between access control unit 1 and lock unit 2does not need to be simultaneous and "online", but can make use ofintermediate carrier media. This makes possible a spatial and temporalseparation of the authorization check 9 from the locking procedure 5.Together with the employment of a telephone connection this allows e.g.a simple and cost saving bridging of distances of any size, between acentral access control unit 1 and a plurality of arbitrarily locatedlocking devices 2, as will be described in a later example.

The invention thus makes possible the setting up of a hire system whichhas the following possibilities and advantages:

complete automation, and therewith cost reduction and 24-hour operation;

decentral distribution of the hire stations or of the objects of use;

central, simple administration of frequently changing user authorizationrelationships;

processing of hire procedures without physical transfer of keys ordocuments.

In the following there will be described an example of employment of theinvention:

An automated bicycle hire system is involved, with which there is madepossible, for a registered group of users, access to a number ofarbitrarily located bicycles in an area, at any time, whereby use datais to be detected for reasons of security and for the purpose ofbilling. Hiring out and return are effected by means of communicationwith a computer via telephone.

The locking device 2 consists in a bicycle lock which has the propertiesaccording to the invention: the input medium is a keypad, the outputmedium a e.g. six character LCD display. In the locked condition, thebicycle cannot be moved, which can be additionally ensured in that anappropriate alarm device in accordance with the state of the art isintegrated which is activated upon locking. In the unlocked condition,the alarm device is deactivated and the bicycle can be moved and ridden.

The access control unit 1 consists in a computer system which isconnected with telephone lines via conventional modems. The control anddata input by a calling user is effected by means of multi-frequencydialling tones, which one can generate with most telephones via thetelephone keys or with cheap, common auxiliary devices. Such computersystems are state of the art, e.g. in automatic telephone bankingsystems.

A cycle of use runs as follows:

The bicycles are, as agreed, deposited in the vicinity of telephone callboxes. The user locates such a deposited bicycle and wishes to use it.For this purpose he reads a bicycle number and, from the LCD display onthe locked lock, a further number. The combination of these numbersconstitutes the code request code 3. With this information he enters thetelephone call box and calls the access control computer 1. Thisrequests him to input his user number, his secret number (PIN) (9), andthe combined code request code 3, consisting of the bicycle number andthe number indicated on the lock. The user data is checked, the codedrequest code 3 compared, if appropriate, with the stored condition dataof the bicycle concerned, the authorization for use of this bicycle ischecked, the new hire condition stored and the multiple-characteropening code 4 associated with this bicycle and the current use cycle isdetermined. This opening code 4 is then communicated to the useracoustically. The bicycle concerned is thereupon regarded, in accordancewith contract, as hired by the user concerned. The user can now open thelock by input of the opening code 4 and then use the bicycle. During theuse, he can close the lock at any time and again open it through renewedinput of the opening code 4. The code request code 3 displayed on theLCD display is blanked during the use cycle and in its place anindication 3* displayed, which indicates to a potential subsequent userthat this bicycle is already in use. At the end of the use, the userdeposits the bicycle again, in accordance with the agreement, e.g. inthe vicinity of a telephone call box. He closes the lock, presses aspecial end key and once again enters the opening code 4. The lockinterprets the combination of end key and opening code 4 as the input ofthe end code 6. Thereupon it switches to a new use cycle and carries outthe code switching (4→4') whereby the confirmation code 8 is displayedon the LCD display. This confirmation code 8 of the previous use cycleis at the same time the new code request code 3', which will be found bythe next user. For the user, the confirmation code 8 serves, with regardto the access control computer 1, as proof that the use has ended. Acontinuing use with the old opening code 4 is, of course, not possibleafter the code switching. Thus, the user again enters the telephone callbox, calls the access control computer 1, identifies himself to thiscomputer and enters the confirmation code 8. The computer compares thiswith the stored, expected code, and in the case of correspondency thebicycle is registered as returned. The use data can thereby be storedfor billing purposes. Further, it is also conceivable that the user willbe asked to enter the location number of the telephone call box in whichhe is, so that the computer can determine the location of the bicycleconcerned therefrom, with the aid of a corresponding directory. Further,the computer can offer an information function so configured that uponinput of a present location by means of the telephone call box locationnumber or the user's own telephone number, the location of the nearestbicycle is determined and given out.

The advantages of the described system with regard to manual systems arefound in the temporal and spatial independence of hiring out and return.The advantages in comparison to existing automatic systems lie in theindependence of the return location and the simple administration of theaccess authorizations by means of a central computer, and in simplebilling and effective, complete control.

The procedure described in the above example can be applied to otherfields of use.

Clearly, application for car sharing clubs, hire car fleets or companyvehicle fleets is possible. In the following there will be described anexemplary embodiment for a car sharing club.

Each customer or club member has a special club key. This is constitutedas follows: a mechanical key bit, identical for all club keys,mechanically unlocks the steering wheel locks of all vehicles, whichlocks all lock in the same manner. In the interior of the club key thereis a microchip which releases the electronic immobilizer. An infraredinterface serves for communication with the central locking system. Thisspecification corresponds to the state of the art in new vehicles.Additionally, the key has a small keypad and a multi-frequency tone codetransmitter, as is state of the art for hand transmitters for the remotecontrol of telephone answering machines.

The vehicle use functions as follows: the user calls, from anytelephone, the central reservations office. He activates the club key bymeans of the input of a key PIN. Authentication with regard to theaccess control unit 1 in the central reservations office is effected inthat the customer holds the code transmitter of the club key to themouthpiece and presses a special key. The club key transmits to thecentral reservations computer, by multi-frequency signal, anauthentication code. After checking of access authorization, the openingcode 4 is acoustically indicated to the user. The user enters this codevia the key's keypad. The club key is now primed. Alternatively, thetransfer of the opening code 4 from the reservations computer 1 to theclub key could be effected by multi-frequency signalling. This would,however, require higher technical outlay for the club keys, many ofwhich will be present. A securing of the transferred code againstunauthorised monitoring (bugging) can be readily implemented by means ofcryptographic means. Thus, e.g. it can be ensured that the opening codeis valid only for a particular club key.

In the vehicle, the features of the invention can be implemented bymeans of software adaption in the central locking and immobilizercontrol unit: the central locking opens upon input of the currentlyvalid opening code 4 by infrared signal. The immobilizer releases theignition circuitry upon receipt of the currently valid opening code 4from the club key microchip. Cryptographic securing methods (codeswitching, public-private key encryption), as are state of the art forcommunication between the club key and the central locking orimmobilizer, can be integrated into the code exchange principle inaccordance with the invention: within a user cycle the locking functionacts for interim locking and re-opening in a conventional manner. Theend of the use cycle is initiated by the user by means of pressing of aspecial end key on the club key. The end code 6 is transferred to thecentral locking system by infrared signal. The central locking systemeffects the code switching (4→4') and re-transmits the confirmation code8.

Additionally, there is a clear possibility for the transfer ofreservation and trip information. There may be contained in the openingcode 4, or transferred with it, e.g. information about a maximum useperiod, the immobilizer blocking the ignition if this period isexceeded. There may be contained in the confirmation code 8, ortransferred with this code, e.g. information about the distancetravelled, exceeded maximum speeds or information concerning accidents,impacts or other irregularities delivered from an accident datarecorder. A GPS satellite navigation system may determine the actualreturn location and transfer this in a manner secure from manipulation.

The confirmation code 8 and the transferred additional data areintermediately stored in the microchip of the club key. The return ofthe vehicle functions analogously to the hiring out. The customer callsthe central reservations office and transfers via the multi-frequencycode transmitter of the club key the intermediately stored confirmationcode 8 and possibly also additional data, to the reservations computer.There, the data is evaluated and stored and the vehicle registered asreturned.

The advantages of the described system are the following:

The greatest advantage is the absence of a need for central hiringstations. The vehicles can be left at arbitrary locations. This expandsthe circle of users, increases acceptance and reduces costs.

Advantageous in comparison with conventional manual hiring procedures isthe removal of the labour-intense administrative effort forauthorization checks, vehicle key issuing, registration, key return,data collection and data processing.

Advantageous with regard to the procedures widely practised in carsharing clubs is the removal of the significant security risk and thelack of control, which arise due to the employment of a central safewhich contains the keys of all vehicles and to which all participantshave a key. An additional advantage is the automatic, directregistration of trip data, which can be evaluated directlycomputer-aided. The inconvenient use of vehicle log books is not needed.

Advantageous for the user in comparison to competing systems is that heneed not have a chip card and need not operate an on-board computer. Forhim, after the priming of the club key, the vehicle use functions aswith a private vehicle. He opens the central locking, starts theignition and drives away. Advantageous for the operator is the absenceof investment in on-board computer hardware.

Advantageous in relation to credit card based automatic machine systemswith key safes, is the simplified and speeded-up procedure involved. Forthe operator the in vestment and main tenance costs for automaticmachines and key safes are not needed.

Advantages with respect to competing solutions on the basis of dataconnections via radio networks are cost savings for radio hardware andtransmission fees, lack of dependence upon particular locations andsecurity against system failure.

A further possible application for decentral objects of use is describedin the last example. In a copy shop, a largely automated operation is tobe made possible and high cost investments in additional hardware forbilling purposes, in relation to the multiply present copyingapparatuses, are to be avoided. One realisation of these requirementscould be as follows:

Billing a nd money collection is effected by means of a centralautomatic machine, of which only one is present, which accepts a depositand issues an opening code for a particular copying apparatus. Therequired functionality on the part of the apparatus can be integrated bymeans of a simple control software adaptation without mechanicalmodification, in the copying apparatus, in a cost effective manner.Cabling of the individual apparatuses with central counters is notnecessary, and neither is the installation of coin-operated machines orcard readers at the apparatuses. Through input of the opening code, theapparatus is set in function for a maximum number of copies and time, bymeans of additional data coded therewith. In the finally-obtainedconfirmation code, the actually used copies are coded in, from which thecentral unit, together with the time spent, calculates the fees andreturns the remaining deposit.

What is claimed is:
 1. In a system for the controlled, time-restricteduse of objects of use with a locking device and an access control unit,a method comprisingthe access control unit (1) issuing an opening code(4), the locking device (2) receiving the opening code (4) to unlock anobject of use controlled thereby, inputting an end code (6) into thelocking device for ending use of the object, and the locking deviceoutputting a confirmation code (8) and changing the opening code (4→4').2. A method according to claim 1, further comprising inputting a coderequest code (3) from the locking device to the access control unit (1).3. A method according to claim 2, wherein the confirmation code 8 of afirst use cycle n is the same as a next code request code (3') of a nextuse cycle n+1.
 4. A method according to claim 3, wherein additional datais contained in the opening code output from the access control unit. 5.A method according to claim 3, wherein additional data concerning theobject of use is contained in the confirmation code and/or in the coderequest.
 6. A method according to claim 2, further comprising checkinguse authorization (9) for the object of use with the access control unit(1).
 7. A method according to claim 2, wherein the end code is relatedto the opening code in a defined manner.
 8. A method according to claim2, wherein additional data is contained in the opening code output fromthe access control unit.
 9. A method according to claim 2, whereinadditional data concerning the object of use is contained in theconfirmation code and/or in the code request.
 10. A method according toclaim 1, further comprising checking use authorization (9) for theobject of use with the access control unit (1).
 11. A method accordingto claim 10, wherein the end code is related to the opening code in adefined manner.
 12. A method according to claim 10, wherein theconfirmation code 8 of the use cycle n is the same as the code requestcode of the use cycle n+1.
 13. A method according to claim 10, whereinadditional data is contained in the opening code output from the accesscontrol unit.
 14. A method according to claim 10, wherein additionaldata concerning the object of use is contained in the confirmation codeand/or in the code request.
 15. A method according to claim 1, whereinthe end code (6) is related to the opening code (4) in a defined manner.16. A method according to claim 15, wherein the confirmation code 8 ofthe use cycle n is the same as the code request code of the use cyclen+1.
 17. A method according to claim 15, wherein additional data iscontained in the opening code output from the access control unit.
 18. Amethod according to claim 15, wherein additional data concerning theobject of use is contained in the confirmation code and/or in the coderequest.
 19. A method according to claim 1, wherein additional data iscontained in the opening code (4) output from the access control unit.20. A method according to claim 19, wherein additional data concerningthe object of use is contained in the confirmation code and/or in thecode request.
 21. A method according to claim 1, wherein additional dataconcerning the object of use is contained in the confirmation code (8)and/or in the code request code (3).
 22. A locking device for objects ofuse, which are to be used for a particular period of time by a user, thelocking device comprising:means for unlocking the locking device inresponse to an opening code; and means for altering the opening code andissuing a confirmation code in response to an end code, hereby theconfirmation code serves as proof of the ending of the use; wherein thelocking device issues a confirmation code and changes the opening codein response to an end code.
 23. A locking device according to claim 22,wherein locking device further includes means for transferring data thatcorresponds to the opening code and the end code.
 24. A locking deviceaccording to claim 23, wherein the means for transferring data iscomprised of a keypad and display on the locking device.
 25. A systemfor locking objects of use, which are to be used for a particular periodof time by al user, comprising:a central access control unit; and atleast one locking device; wherein the locking device provides a cycle ofuse in which a locking device provides a request code from which thecentral access control unit issues an opening code that enables the userto open the locking device; and in which the locking device provides aconfirmation code upon receipt of an end code and changes the openingcode.
 26. A system according to claim 25, wherein the confirmation codeis provided to the central access control unit to serve as proof of theend of use of an object controlled by the locking device.
 27. A systemaccording to claim 25, wherein the central access control unitdetermines whether the user is authorized to use an object controlled bythe locking device upon receipt of the request code.
 28. A systemaccording to claim 25, wherein the end code is related to the openingcode in a defined manner.
 29. A system according to claim 25, whereinthe confirmation code serves as the code request code for a nextsubsequent cycle of use.
 30. A system according to claim 25, wherein theopening code includes additional data by which the number of uses of theobject controlled by the locking device, the period of use of the objectcontrolled by the locking device, or the type of use of the objectcontrolled by the locking device, can be restricted.
 31. A systemaccording to claim 25, wherein the confirmation code and/or the requestcode includes additional data regarding the object controlled by thelocking device.